Dilator and introducer assembly

ABSTRACT

A resiliently flexible body vessel or body cavity dilator that tapers toward one end and a transition zone that decreases in flexibility along the dilator away from the one end. The dilator can comprise a dilator arranged to be slid over a guidewire for use in the placement of an intraluminal graft bridging an aortic aneurysm. The dilator can also comprise an inner core of relatively stiff material surrounded by an outer layer of resiliently flexible material.

FIELD OF THE INVENTION

The present invention relates to a body vessel or cavity dilator and toan introducer assembly for dilating a vessel or cavity and introducing asheath therein.

BACKGROUND ART

There are many applications where it is necessary to insert a sheath orcatheter into a body cavity or vessel. One means of facilitating theinsertion of a sheath is to use a dilator fitted with a sheath thatmoves into the cavity or vessel and is then withdrawn leaving the sheathin place.

The placement of prosthetic devices, such as stents and grafts,intraluminally and the conduct of minimally invasive operativeprocedures has grown dramatically in recent years. Where, for example,an intraluminal graft is adapted for insertion into a patient to achievebridging and occlusion of an aortic aneurysm, a sheath of sufficientdiameter and adapted to assist with the delivery of the prostheticdevice needs to be inserted into and through the femoral and associatediliac artery.

In many persons, the femoral artery, in passing over the pelvis, takes aquite tortuous path that can impede the passage of a catheter ofsufficient width and stiffness and in turn also impede the travel of agraft through the catheter.

The present invention is directed to a device that alleviates theproblem posed by such tortuous vessels.

STATEMENT OF INVENTION

According to a first aspect, the present invention comprises aresiliently flexible dilator for a bodily vessel, the dilator taperingtowards one end to facilitate insertion of the dilator into the vesseland having a transition zone having a first end proximate the said oneend and a second end distal the said one end, the physical properties ofthe dilator in the transition zone being such that the flexibility ofthe dilator at the second end of the transition zone is less than theflexibility of the dilator at the first end of the transition zone.

In one embodiment, the transition zone of the dilator comprises no morethan half the length of the dilator, and more preferably no more than aquarter the length of the dilator. The resilient flexibility of theremainder of the dilator, apart from the transition zone, is preferablysubstantially constant along its length.

The dilator can taper along its whole length or just a portion adjacentthe said one end. The tapering portion of the dilator towards one endcan comprise a frusto-conical portion or hemispherical portion adjacentthe said one end. The transition zone of the dilator can further overlapor be separate from the tapering portion of the dilator.

In one embodiment, the dilator is comprised of a polymeric orelastomeric material. The change in flexibility in the transition zonecan be provided by an increase in cross-linking of the polymeric orelastomeric material along the dilator.

In another embodiment, the transition zone comprises an inner relativelystiff core of material having a tapered portion, with at least thetapered portion being surrounded by an outer layer of relativelyresiliently flexible material that extends beyond the tapering portionof the core material so that the dilator undergoes a gradual decrease inflexibility in the region of the tapering portion of the core. In thisembodiment, the dilator adjacent the said one end of the dilator can beformed from the relatively resiliently flexible material. Thisembodiment of the dilator can be fabricated by a co-extrusion of theinner core and the outer layer. The core can be fabricated from a 90/10high density polypropylene and the outer layer from an ethylene-vinylacetate (EVA) copolymer. Both the core and outer layer call include abarium sulfate component (eg: approximately 10%) to make the sameradiopaque.

In a preferred embodiment, the dilator has a longitudinally extendingaxial bore to receive a guidewire already inserted through a vessel, andhas a sheath disposed thereabout so that when the dilator is withdrawnthe sheath is left in place in the vessel.

The flexibility of the said one end of the dilator is preferablysubstantially similar to the flexibility of the guidewire insertedthrough the dilator. The flexibility of the transition zone preferablygradually decreases from the first end to the second end of thetransition zone until the flexibility is substantially similar to theflexibility of the associated sheath.

In a preferred embodiment, the dilator is arranged so as to be insertedinto the femoral and associated iliac artery so as to allow theplacement of a sheath through these arteries for use in the intraluminalplacement of an intraluminal graft bridging an aortic aneurysm. Theguidewire in this embodiment is preferably an Amplatz extra stiff (AES)guidewire of 0.035" diameter.

According to a second aspect, the present invention consists in anintroducer assembly for introducing a sheath into a bodily vesselcomprising a guidewire, a resiliently flexible dilator tapering towardsone end and a longitudinally extending axial bore that can receive theguidewire, and a sheath positioned around the dilator, the dilatorhaving a transition zone having a first end proximate the said one endand a second end distal the said one end, the physical properties of thedilator in the transition zone being such that the flexibility of thedilator at the second end of the transition zone is less than theflexibility of the dilator at the first end of the transition zone.

Preferably, the said one end of the dilator has a flexibilitysubstantially similar to that of the guidewire. The flexibility of thetransition zone preferably gradually decreases from its first end to itssecond end, the second end having a flexibility substantially similar tothe flexibility of the associated sheath.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter by way of example only, preferred embodiments of theinvention are described with reference to the accompanying drawings, inwhich:

FIG. 1 is a side elevational view of a dilator according to the presentinvention;

FIG. 2 is a longitudinal cross-sectional view along line II--II of thedilator of FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of the dilator of FIG. 1ready for insertion into a body vessel or cavity over a guidewire;

FIG. 4 is a longitudinal cross-sectional view of another embodiment of adilator according to the present invention;

FIG. 5 is a diagrammatic representation of a ventral view of a patienthaving all aortic aneurysm bridged by a trouser graft; and

FIGS. 6A-6C show stages of using a dilator according to the presentinvention to insert a sheath into and along a femoral artery, being theinitial steps in inserting a trouser graft intraluminally into a patienthaving an aortic aneurysm.

PREFERRED MODE OF CARRYING OUT THE INVENTION

A resiliently flexible dilator for a vessel according to the presentinvention is generally depicted as 10 in FIGS. 1 and 2. The dilator 10comprises a substantially cylindrical shaft 11 and a tapering portionadjacent the end 12 and a longitudinally extending axial bore 13.

In the embodiment depicted in FIGS. 1 and 2, the dilator 10 isfabricated from a elastomeric material. In a transition zone (depictedgenerally as 14) proximate the end 12, the cross-linking of theelastomeric material increases away from the end 12 so leading to adecrease in the flexibility of the elastomeric material in the region 14away from the end 12. The resilient flexibility of the remainder of thedilator 10 is substantially constant.

In the embodiment of the dilator depicted generally as 20 in FIG. 4, thedilator 20 comprises a relatively stiff core 21 of 90/10 high densitypolypropylene, having a tapering portion 22, surrounded by a relativelyresiliently flexible EVA copolymer outer layer 23 that extends beyondthe tapering portion 22 of the core 21 and is used to form the dilatoradjacent the end 12. The tapering portion 22 of the core 21 results in agradual decrease in flexibility of the dilator 20 in the region of thistaper 22 between the end 12 and the remainder of the dilator 20. Boththe core 21 and the outer layer 23 include a barium sulfate component ofabout 10% to make them radiopaque. Those of ordinary skill in the artwill recognise that materials possessing similar characteristics tothose previously described may alternatively be used to fabricate thecore 21 and outer layer 23.

The dilator 10 or 20 can form part of a sheath introducer assemblygenerally depicted as 30 in FIG. 3. The introducer assembly 30 isadapted to place a sheath 31 through and within a tortuous blood vessel.The assembly 30 comprises a guidewire 32 that passes through the bore 13of the dilator, and the sheath 31.

An example of an application where a dilator and an introducer assemblyaccording to the present invention are specially beneficial is in theplacement of intraluminal grafts into a patient to achieve bridging andocclusion of an aortic aneurysm.

As is seen in FIG. 5, the aorta 40 is connected to the left and rightiliac arteries 41 and 42. In FIG. 5, the aortic aneurysm 45 is locatedbetween the renal arteries 43 and 44 and extends down the left iliacartery 41. One means of bridging the aneurysm 45 is to use a trousergraft 46 that is provided with a bifurcation to form a pair of shorttubular extensions 46a and 46b that extend down the iliac arteries 41and 42 respectively.

The method for positioning a sheath 31 into each of the iliac arteries41 and 42, being one of the steps necessary to successfully place theintraluminal graft 46 in position within the aorta 40 will now bedescribed with reference to FIGS. 6A-6C. In carrying out the method anincision is made to expose one of the femoral arteries (ipsilateral),which flows from the corresponding iliac artery, and using the Seldingerneedle technique, a 0.035" diameter floppy tipped flexible guidewire isinserted into and through the femoral artery and then the iliac artery42 into the aorta 40 such that it transverses the aneurysm 45. An 8French haemostatic sheath is then introduced over the guidewire tocontrol bleeding. An angiographic catheter is introduced to allow anangiogram to be taken of the patient to shown the position of the renalarteries 43, 44 and other relevant anatomical structures of the patient.

An Amplatz extra stiff (AES) guidewire 32 (0.035" diameter) is thenpassed through the angiographic catheter into the aorta 40. Afterwithdrawal of the angiographic catheter, the stiff guidewire 32 is leftin situ (see FIG. 6A).

A resiliently flexible dilator 20 (as depicted in FIG. 4), with sheath31, preferably of 24 French, is then introduced into the femoral arteryand along the ipsilateral iliac artery 42 (see FIG. 6B). The tapering ofthe dilator towards the end 12 allows the dilator to follow theguidewire 32 through the tortuous portion of the femoral and iliacartery before entering the aorta 40. The gradual decrease in flexibilityprovided by the tapering portion 22 of the dilator core 21 facilitatesinsertion of the dilator 20.

The dilator 20 is pushed through the aorta 40 to proximate the renalarteries 43,44 and then withdrawn leaving the sheath 31 extending acrossthe aorta 40 as depicted in FIG. 6C.

With the sheath 31 in place, a pre-packaged graft 46 can be passedthrough the sheath and appropriately placed in the aorta 40, as isdepicted in FIG. 5.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing front the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

What is claimed is:
 1. A resiliently flexible dilator for a bodilyvessel, the dilator tapering towards one end to facilitate insertion ofthe dilator into the vessel and having a transition zone having a firstend proximate the said one end and a second end distal the said one end,the physical properties of the dilator in the transition zone being suchthat the flexibility of the dilator at the second end of the transitionzone is less than the flexibility of the dilator at the first end of thetransition zone;wherein the transition zone of the dilator comprises atleast one of no more than half the length of the dilator, and no morethan one quarter of the length of the dilator; wherein the flexibilityof the transition zone is gradually decreasing between its first and itssecond end and wherein the flexibility of the dilator apart from thetransition zone has a substantially constant flexibility and furthercomprises an elastomeric material; and, wherein the change inflexibility of the transition zone of the dilator is provided by anincrease in cross-linking of the elastomeric material comprising thetransition zone away from its first end.
 2. A resiliently flexibledilator for a bodily vessel, the dilator tapering towards one end tofacilitate insertion of the dilator into the vessel and having atransition zone having a first end proximate the said one end and asecond end distal the said one end, the physical properties of thedilator in the transition zone being such that the flexibility of thedilator at the second end of the transition zone is less than theflexibility of the dilator at the first end of the transitionzone;wherein the transition zone of the dilator comprises at least oneof no more than half the length of the dilator, and no more than onequarter of the length of the dilator; wherein the flexibility of thetransition zone is gradually decreasing between its first and its secondend and wherein the flexibility of the dilator apart from the transitionzone has a substantially constant flexibility and further comprises anelastomeric material; wherein the change in flexibility of thetransition zone of the dilator is provided by an increase incross-linking of the elastomeric material comprising the transition zoneaway from its first end; wherein the transition zone comprises an innerrelatively stiff core of material having a tapering portion with atleast the tapering portion being surrounded by a relatively resilientlyflexible outer layer that extends beyond the tapering portion of thecore material; wherein the inner core is fabricated from high densitypolypropylene, and the outer layer is fabricated from an EVA copolymer.3. A resiliently flexible dilator for a bodily vessel, the dilatortapering towards one end to facilitate insertion of the dilator into thevessel and having a transition zone having a first end proximate thesaid one end and a second end distal the said one end, the physicalproperties of the dilator in the transition zone being such that theflexibility of the dilator at the second end of the transition zone isless than the flexibility of the dilator at the first end of thetransition zone;wherein the transition zone of the dilator comprises atleast one of no more than half the length of the dilator, and no morethan one quarter of the length of the dilator; wherein the flexibilityof the transition zone is gradually decreasing between its first and itssecond end and wherein the flexibility of the dilator apart from thetransition zone has a substantially constant flexibility and furthercomprises an elastomeric material; wherein the change in flexibility ofthe transition zone of the dilator is provided by an increase incross-linking of the elastomeric material comprising the transition zoneaway from its first end; wherein the transition zone comprises an innerrelatively stiff core of material having a tapering portion with atleast the tapering portion being surrounded by a relatively resilientlyflexible outer layer that extends beyond the tapering portion of thecore material; wherein the inner core is fabricated from high-densitypolypropylene; the outer layer is fabricated from an EVA copolymer;wherein the dilator has a longitudinally extending axial bore to receivea guidewire already inserted through the vessel, and has a sheathdisposed thereabout so that when the dilator is withdrawn from thevessel the sheath is left in place in the vessel; wherein theflexibility of the guidewire at said one end and the first end of thetransition zone are substantially similar to the flexibility of theguidewire, and; wherein the flexibility of the second end of thetransition zone is substantially similar to the flexibility of theassociated sheath.
 4. An introducer assembly for introducing a sheathinto a bodily vessel comprising a guidewire, a resiliently flexibledilator tapering towards one end of a longitudinally extending axialbore that can receive the guidewire, and a sheath positioned around thedilator, the dilator having a transition zone having a first endproximate the said one end and a second end distal the said one end, thephysical properties of the dilator in the transition zone being suchthat the flexibility of the dilator at the second end of the transitionzone is less than the flexibility of the dilator at the at the first endof the transition zone, and;wherein the one end of the dilator has aflexibility substantially similar to the guidewire.
 5. A medicaldilator, comprising an elongate shaft that is flexible along its entirelength from a proximal end to a distal end, the shaft having asubstantially cylindrical outer surface from the proximal end to atapered portion adjacent the distal end and an axial bore from aproximal end to the distal end, the shaft further including a transitionzone having an axial length located adjacent the tapered portion, thetransition zone exhibiting a gradual decrease in flexibility along itsaxial length in the proximal direction, the elongate shaft having asubstantially constant flexibility proximal to the transition zone. 6.The dilator of claim 5, wherein the shaft is made of an elastomericmaterial, and wherein the gradual decrease in flexibility in thetransition zone is provided by an increase in cross-linking of theelastomeric material in the proximal direction within the transitionzone.
 7. The dilator of claim 5, wherein the shaft comprises an innercore having a tapered distal end that terminates at an axial locationadjacent the tapered portion of the shaft, and an outer layersurrounding the core along its length and extending beyond the tapereddistal end of the core to define the tapered portion of the shaft, theouter layer being relatively more flexible than the inner core, andwherein the gradual decrease in flexibility in the transition zone isprovided by the increasing cross-section of the core along its tapereddistal end.